A 15th-century astrologer from China made it into space on a throne powered by 47 bamboo rockets.

busted

The combined heat from all 47 bamboo rockets caused them to explode, nearly destroying the throne and doing significant damage to the stand-in astrologer (Buster) before it ever got off the ground. A throne powered by 47 modern rockets shot violently to one side, due to uneven firing, but would not have had the thrust to lift the chair very far at all, let alone all the way into space.

A free energy device can be made to harness enough energy to power a house.

busted

Free energy itself is a scientific fantasy. Almost all of the free energy devices the MythBusters built consumed more energy than they produced and the one ‘successful’ device only produced enough electricity to power half a wrist watch, and was ridiculously large for such a small amount of energy. One test, cut for time and shown on MythBusters Outtakes involves coils of baling wire being used to siphon off electricity from nearby PG&E power lines in the Santa Cruz Mountains.

A regular house fan can cause decapitation.

busted

Normal household fans do not have the power to even inflict serious injury while spinning at top speed – they are more likely to break first. An industrial fan is capable of inflicting a fatal injury, but is not powerful enough to take a head off. Even a purpose-built razor-sharp, stainless steel fan powered by a lawn mower engine could not completely sever a head from the neck.